Editorial For reprint orders, please contact: reprints@futuremedicine.com Nanocytotoxicity using matrix-assisted laser desorption ionization mass spectrometry Hani Nasser Abdelhamid* ,1 1 Advanced Multifunctional Materials Laboratory, Department of Chemistry, Assiut University, Assiut 71516, Egypt *Author for correspondence: hany.abdelhamid@aun.edu.eg “ The analysis of bacteria species using MALDI-MS is simple and fast compared with traditional analysis methods such as cell culture, which requires days and sometime weeks. ” First draft submitted: 15 September 2019; Accepted for publication: 27 February 2020; Published online: 6 April 2020 Keywords: antibacterials • matrix-assisted laser desorption ionization mass spectrometry • nanocytotoxicity • nanomedicine Humans are usually in contact with pathogenic bacteria and this is an increasing cause of mortality [1,2]. Conse- quently, a broad range of analytical methods has been investigated for the taxonomic classification and identification of bacterial strains [3–8]. Some of these methods are expensive, have a lack of high selectivity and are insensitive for low concentrations [3–7]. On the other hand, mass spectrometry (MS), the detection of analyte after ionization using an energy source (energetic particles, electron, laser, etc.), has several advantages such as being high through- put, having high sensitivity and good selectivity for bacteria and other microorganisms [3–7]. Among several MS methods, soft ionization mass spectrometry such as matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) [9] have been used intensively nowadays to ionize thermal labile analytes such as proteins without or with minimal fragmentation [10–13]. Both methods can be easily applied in microbiology laboratories for either academic or commercial purposes. MALDI-MS procedure offers a straightforward diagnostic method ensuring the robust detection of many thermal labile biomolecules in pathogenic bacteria without significant fragmentation [14]. Furthermore, it can be used for the identification of bacteria and bacterial species in complex samples such as a bacterial mixture and bloodstream infections. The analysis of bacteria species using MALDI-MS is simple and fast compared with traditional analysis methods such as cell culture, which requires days and sometime weeks. Nanotechnology, technology implementing nanoparticles with a dimensional of nano size (<100 nm, nm = 10 -9 m), has been integrated into several applications offering high performance [15–24]. The global market of nanotechnology involved hundreds of billions of US dollars every year. Among the wide applications of nanoparti- cles, they have been used as antibacterial agents [25,26]. Nanotoxicology has been defined as “the study of the adverse effects of engineered nanomaterials on living organisms and the ecosystems, including the prevention and amelioration of such adverse effects” [27–29]. Nanoparticles offer high cytotoxicity toward pathogenic bacteria. They show higher effi- ciency compared with traditional antibacterial agents and can effectively kill bacteria without observable resistance. In addition, they can be easily implemented in recent technologies such as thin films, devices and more. Evaluation of the antibacterial activity of a nanoparticle using MALDI-MS is promising for the rapid analysis of nanocytotoxicity. MALDI-MS identified bacteria via their biomolecules such as proteins and nucleic acids. Thus, a simple comparison of the mass spectra for a certain bacterial species before and after incubation with the nanoparticles can be tested to decide the nanoparticle’s antibacterial activity. The analysis can be performed with and without extract of the bacterium’s content. Analysis of the bacterium without extraction is usually called intact cell analysis. MALDI-MS can be used efficiently to detect signals of abundant molecules of the bacterial cells simultaneously without significant ionization suppression. The mass spectrum can be used as a fingerprint for each species. The signals can also be used for monitoring the changes in the bacteria biomolecules via comparison with a reference or via pattern matching with the database. The differentiation of closely related bacteria using MS spectra can be improved via treating bacteria cells with the protease trypsin. The changes in mass signals upon interactions Future Microbiol. (Epub ahead of print) ISSN 1746-0913 10.2217/fmb-2019-0260 C  2020 Future Medicine Ltd